James Clark d0774cf730 perf: Always wake the parent event ... [ Upstream commit 961c39121759ad09a89598ec4ccdd34ae0468a19 ] When using per-process mode and event inheritance is set to true, forked processes will create a new perf events via inherit_event() -> perf_event_alloc(). But these events will not have ring buffers assigned to them. Any call to wakeup will be dropped if it's called on an event with no ring buffer assigned because that's the object that holds the wakeup list. If the child event is disabled due to a call to perf_aux_output_begin() or perf_aux_output_end(), the wakeup is dropped leaving userspace hanging forever on the poll. Normally the event is explicitly re-enabled by userspace after it wakes up to read the aux data, but in this case it does not get woken up so the event remains disabled. This can be reproduced when using Arm SPE and 'stress' which forks once before running the workload. By looking at the list of aux buffers read, it's apparent that they stop after the fork: perf record -e arm_spe// -vvv -- stress -c 1 With this patch applied they continue to be printed. This behaviour doesn't happen when using systemwide or per-cpu mode. Reported-by: Ruben Ayrapetyan <Ruben.Ayrapetyan@arm.com> Signed-off-by: James Clark <james.clark@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20211206113840.130802-2-james.clark@arm.com Signed-off-by: Sasha Levin <sashal@kernel.org>		2022-02-16 12:54:20 +01:00
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callchain.c
core.c	perf: Always wake the parent event	2022-02-16 12:54:20 +01:00
hw_breakpoint.c
internal.h	perf: Optimize get_recursion_context()	2020-11-09 18:12:34 +01:00
Makefile
ring_buffer.c
uprobes.c	kernel: delete repeated words in comments	2022-02-01 17:25:45 +01:00